MONTPELIER — Vermont lawmakers return this week for the second half of their 2013 legislative session with an already uncertain financial picture having grown even more clouded with threatened federal budget cuts.

But money is only one of the puzzles lawmakers are hoping to solve in the eight weeks remaining on their schedule. Dozens of items are likely to get attention before the expected May adjournment, including bills decriminalizing marijuana, allowing terminally ill patients to end their lives with a doctor’s help, and helping to smooth the transition from state-subsidized health care to the health insurance marketplace called for under the federal Affordable Care Act.

Education programs, low-income heating assistance and a host of other programs face federal funding cuts unless Washington resolves an impasse that began automatic cuts in both defense and domestic programs on March 1.

The federal cuts cast a big cloud over a session that began with Gov. Peter Shumlin and lawmakers hoping to pay for big ticket items including expanded child care subsidies for low-income working families and expanded state support for energy-saving efforts including insulating homes and reducing demand for heating fuel.

Hopes appear to be fading for big new spending.

“One thing is clear. We’re not going to be able to do all the things we would like to do,” said Rep. Janet Ancel, D-Calais, who is chairwoman of the tax policy-writing House Ways and Means Committee. “We’re going to have to make some choices,” she said.

The Low-Income Home Energy Assistance Program is an example of something in which federal budget troubles spell big problems for the state’s already tight finances.

When he released his budget in January, Shumlin proposed using $6 million from a new tax on “break-open tickets” to make up for dwindling federal support for heating assistance. The betting tickets are sold at bars and social clubs and raise money for a range of charities in the state. Bettors break or rip them open and see if symbols printed on the inside match those on the outside. Shumlin said the new tax would raise $17 million, with some of the money also going for renewable energy and home weatherization programs.

But since then, the Legislature’s Joint Fiscal Office has estimated the tax would raise only about $6.5 million, and some lawmakers are even skeptical of that figure. Meanwhile, Ancel said members of that tax-writing panel were worried about the effects a new tax would have on the charitable fundraising efforts of the nonprofit groups.

Similar doubts are cropping up about a plan for a penny-per-ounce tax on soda and other sugar-sweetened beverages to pay for health programs. Shumlin has expressed strong opposition to the tax, saying it would send retail sales out of state. But the House Health Care Committee approved a bill — now in Ways and Means — that would use that money to help cushion the sticker shock some Vermonters are expected to see when they switch from state- to federally-subsidized health care.

There also appears to be strong legislative opposition to Shumlin’s proposal to use savings from reducing earned income tax credit benefits for the working poor to pay for expanded child care subsidies.

While the money puzzle grows more difficult, lawmakers also may have lost ground in efforts to pass a bill whose supporters were hopeful in January — the measure to allow doctors to prescribe lethal doses of medication to terminally ill patients who request it.

The Senate passed a much shorter, substitute bill that absolves doctors and family members from civil and criminal liability when such a patient ends her or his own life. If the House passes a bill, it’s expected to be closer to the original Senate version, in which case a conference committee would have to work out the differences.